It's easy to see how these anomalously low temperatures have contributed to the steep decline in the percentage of Americans who say they believe in global warming. According an October 2009 poll by the Pew Research Center, only 57 percent of Americans believe that there is solid evidence that the earth is warming, down from 71 percent in April 2008.

Nobody said it would never get cold again

No sane climate scientist would say that global warming means never having another severe cold snap. What it does mean is a gradual shifting of the odds away from record-breaking cold days and toward record-breaking hot ones.

And that's exactly what we're seeing, even though we still get the occasional Arctic blast. The National Center for Atmospheric Research, a nongovernmental research group based in Boulder, Colo., released a report in November showing that, in the continental United States, the ratio of record high temperatures to low temperatures has increased dramatically in recent decades. In the 1950s, the center reports that ratio slightly exceeded 1 to 1, meaning that there were about as many record-breaking cold days as there were hot ones. By the 2000s, there were twice as many record highs as lows. On a warming planet, we'll still get the lows, just not as often.

But what's particularly troubling is that, even though temperatures have been high, the sun has been throwing a little less heat our way lately. According to NASA, we are currently experiencing the lowest solar minimum in nearly a century. Nobody knows when the sun will resume its previous output – in the 17th century, the sun went into a 70-year lull that correlated with cooler temperatures on Earth – and there's a chance that it may never come back.

Yet, the world is still warming. If and when the sun does reverse its downturn, we'll get a more accurate sense of how much of a mess we've made of our planet's climate.

As for the current frigid conditions, you can blame something called the Arctic Oscillation, a halo of counterclockwise winds blowing around the top of the world. When these winds are strong, they lock the cold air in place up there. But when the winds are weaker, the Arctic air slides southward, across the Norhern Hemisphere, and through the gaps in your windows where it eventually settles on your spouse's feet at night.

The New York Times's Andrew Revkin noted Monday that the Arctic Oscillation has entered the deepest cold phase since 1950, although there were times in the 1960s, '70s, and '80s that it came close. Mr. Revkin notes that this phenomenon is one of the least understood atmospheric patterns, but the graph he provides show a clear, if slight, trend: the conditions that brought about this week's freeze are getting less and less likely.

Editor’s note: The Monitor's Environment section has a new URL. And there's a new URL for its Bright Green blog. We hope you'll bookmark these and visit often.